Thread: Advice on table design

The reference I'm quoting from uses imperial / US measurements and I've used a soft conversions where 1" = 25 mm.

dining place settings should be between 24" and 30" wide and 12" to 18" deep. That's 600 to 750 wide and 300 to 450 deep.
So to seat 6, a table should be a minimum of 60" (1500) long (2 x 24" on each side + 2 x 12" at each end), though a more comfortable table would be 84" (2100) long -- adopting 27" x 15" place settings. Width wise 42" (1050) is more sociable than 960 mm, with 48" (1200) considered a maximum. Wider tops allow for plates of food and decorations to be easily placed on the table.
The hoop legs should be placed 14" to 18" (350 to 450) from each end -- a longer top will make achieving this without intruding on the space needs of those sitting at the sides of the table.

Hoop legs in timber are difficult to get strong unless you are good at making tight fitting finger or dovetail joints. These could be machine cut.

A 35 mm thick top will be strong enough, provided you don't plan on using the table as part of a scaffold frame or a means of reaching that light fitting that is otherwise just out of reach.
I'd attach the hoop legs withing a 15 mm deep tight fitting recess to help control racking. If that sounds too hard or flimsy, I'd look at incorporating a batten down the center of the underside to control racking.

1. That doesn't matter, the glue will be perfectly strong enough to support it.
2. I'd normally say they should be further in from the ends, but given that it's quite a short table they're good where they are.
3. The top will be self-supporting. Over that span you could do Riverdance on top of it and it wouldn't even flex.
4. Definitely strong enough.

My only concern will be as Ian said with racking, but that also depends on what your definition of "strong" is. Loads of tables on the market these days have some pretty bad racking issues but will still do what they are made to do.

If its a show piece or something that hardly ever gets used it'll be strong enough, but if its something kids will be playing near I'd say do something about the racking.

The legs are wide enough that 3 or 4 demon bolts down each side of each leg into some threaded inserts in the top should probably be enough to stop racking

https://www.timbecon.com.au/cabinet-...-bolts-cap-nut
https://www.timbecon.com.au/cabinet-...wn-insert-nuts

Really appreciate the feedback guys.

So I dont actually know what racking means and I tried googling it only came up with shops to buy racks. Is racking lateral movement along the length of the table? Ie I stand on the end and push it and the top moves forward and 'wobbles'?

To counter that I was planning to do 2 boards along the length attached to the hoops but ian said a single board down the middle is sufficient?

Just did it in fusion, a single board down the middle attaching to the hoops with half laps

Untitled.jpg

Hows that look? What is this part called? its technically not an apron right?

I would prefer to just screw this part down and not glue - for easy disassembly - thoughts on that? Could use M8 threaded insert and like 4 bolts?

Youre spot on, racking is any movement that pushes something out of square ie wobbles

Ian was suggesting that you recess the tops of the hoops into the underside of the table top by 15mm to lock the hoops and top together more rigidly than bolts or screws would with the hoops flush mounted.

I believe his other suggestion of a single centreline member on the underside relates to something similar to you sketch above, but on the base of the hoop, rather than the top. This fixes the hoop bases in relation to each other, while the top fixes the hoop tops. Then there is much less possibility of the table racking as the hoops cannot move independently of each other and spread.

I see. I think I would rather try and recess it then to have a beam on the bottom. I suppose its a chance to learn how to use the router - I've only used it once to see if it still worked!

How flat will the router get the base of the recess? How flat does it need to be?

Originally Posted by qwertyu

Really appreciate the feedback guys.

So I dont actually know what racking means and I tried googling it only came up with shops to buy racks. Is racking lateral movement along the length of the table? Ie I stand on the end and push it and the top moves forward and 'wobbles'?

To counter that I was planning to do 2 boards along the length attached to the hoops but ian said a single board down the middle is sufficient?

Just did it in fusion, a single board down the middle attaching to the hoops with half laps

Untitled.jpg

Hows that look? What is this part called? its technically not an apron right?

I would prefer to just screw this part down and not glue - for easy disassembly - thoughts on that? Could use M8 threaded insert and like 4 bolts?

This is how I would suggest the longitudinal brace is arranged -- on edge and centered on the "hoops".
Note that I have not shown any joinery details, but in practice the brace should be lapped into the hoops, and shaped at the ends so that they do not present as vertical knee bangers.
It could be attached to the hoops with with knock down fittings. Done with good (not sloppy) joinery, the brace should really stiffen up your design

Looking at the design I do feel like the brace along the middle as shown by Ian and yourself will stiffen up the design but I don't feel like it'll make that make difference in terms of racking.

Due to the design of the table the pivot points will be where the hoops are attached to the top, so to really minimise racking you'll need to add a brace that will reduce the length of the pivot, eg connecting the two hoops together somewhere along the middle of the hoops, or add side rails to the hoops or corner braces. Obviously this will detract from the simplistic design and probably not the look you're going for.

If it were me I'll play it by ear, if your hoops are well constructed and the connection to the top is solid it may very well be "strong enough" (as you can always add the brace later)

Hi Qwertyu

Nice table. You only mention dominoes for joinery and then others have suggested adding hardware between the hoops and the top to stiffen up the table. One of the most fundamental things to keep in mind when working with wood is that it moves as moisture in the environment changes. Doesn't matter how long its been drying for or how well sealed it is if it wants to move then it will expand and contract across the grain. How much for individual boards is guesswork but info is available for common species. A top like yours could potentially change width by 5mm over a year. Over time (and from bitter experience this could be a very short time) this will crack any glued joint between the top and the hoops or if you use enough hardware it could even cause your top to split. One solution is to use a couple of rails between the hoops as others have suggested to keep the base stiff and then attach the top using a system that will allow the top to move. Buttons are a common option for this but google will give you many others. All that said you could use your original joinery and the top may never move - that's wood for you.

Another vote for the view that the design is too vulnerable to racking. In fact it’s vulnerable to racking in two directions.

Across the short axis, a racking force will tend to distort the square leg assemblies (‘hoops’) into trapezoids. Your design is reliant on the strength of the corner joints to resist this - so how confident are you in your joint work?

A racking force along the long axis will tend to break the hoops free from the table top at their point of attachment. Each hoop, considered separately, appears to be only about 80mm wide, so that is the extent of the surface you can use to resist racking. Again, how confident do you feel about your method of attachment?

Also, you tabletop is quite heavy so it will multiply the forces applied to it after a certain point.

Generally, racking forces are resisted by angle bracing, creating triangles, which obviously can’t be pushed out of shape. I understand that they don’t suit your design goal however.

Personally, I think it’s quite a difficult design for a beginner to get right. I think it would be better scaled down into a consol table or something else that goes through life without great demands being placed upon it. People do horrible things to dining tables.

Cheers
Arron

Another thing - Ross Lambert’s post reminds me that the expansion and contraction going on across the width of the tabletop will prevent it being fixed rigidly to the hoops, adding to the problems with racking.

Cheers
Arrom

I wrote a whole post but it didnt seem to get posted!

Anyway, just wanted to clear some things up. Going to place 20mm deep M8 threaded inserts into the table and oversized holes in the hoops to attach the two. The legs will be the same 35x120mm thick timber. Dominos are for the hoops only.

You guys think switching to 45mm think boards will help?